Wave Optics Test

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Wave Optics Test - 38

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Weekly Quiz Competition

Question 1
1 / -0

The phenomenon of rotation of plane polarized light is called:

A
Kerr effect

B
Double refraction

C
Optical activity

D
Dichroism

Solution

The phenomenon of rotating plane polarized light is known as optical activity and the compounds showing this property are called optically active compounds.
Question 2
1 / -0

Which of the following gives the basis for the observation that the universe is expanding?

A
Newton's law of universal gravitation

B
Red shift of light from other galaxies

C
The fact that every element of atomic number greater than 83 is radioactive

D
The zeroth law of thermodynamics

E
Mass-energy equivalence

Solution

Red shift occurs due to observed elongation of wavelength of light due to Doppler effect from objects going away from the observer. Thus a red shift in the universe suggests that the objects are going away from each other, or the universe is expanding.
Question 3
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A student wants to find if a star if moving away from the earth or towards the earth. Which of the following principle he can use?

A
Newton's law of universal gravitation

B
Red shift of light from other galaxies

C
The fact that every element of atomic number greater than 83 is radioactive

D
The zeroth law of thermodynamics

E
Mass-energy equivalence

Solution

Red shift happens when light from an object increases in wavelength. It occurs whenever a light source moves away from an observer.
Blue shift happens when light from an object decreases in wavelength. It occurs whenever a light source moves toward an observer.
Question 4
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In Young's double slit experiment a minima is observed when path difference between the interfering beam is

A
$$\lambda$$

B
$$1.5\lambda$$

C
$$2\lambda$$

D
$$2.25\lambda$$

Solution

The condition for minimum intensity, when the path difference is a multiple of half wavelengths, i.e., $$d\sin\theta = \left(n+\dfrac 12 \right) \lambda $$
So for the minima, n=1, $$\implies d \sin\theta=1.5\lambda$$
Question 5
1 / -0

Which of the following statement is false:

A
Sound and light wave exhibit interference

B
Sound and light wave exhibit diffraction

C
Light wave exhibits polarization while sound wave does not

D
Sound wave exhibits polarization while light wave does not

Solution

Polarization is a property of waves that can oscillate with more than one orientation. Electromagnetic waves such as light exhibit polarization, as do some other types of wave, such as gravitational waves.
Sound waves in a gas or liquid do not exhibit polarization, since the oscillation is always in the direction the wave travels.
Question 6
1 / -0

The light beams of intensities in the ratio of $$9:1$$ are allowed to interfere. What will be the ratio of the intensities of maxima and minima?

A
$$3:1$$

B
$$4:1$$

C
$$25:9$$

D
$$81:1$$

Solution

The light beams with intensities being in the ratio $$\dfrac{9}{1}$$, so the amplitudes are in the ratio $$\dfrac{3}{1}$$. So, the maximum and minimum intensities are in the ratio $$\dfrac{(3+1)^2}{(3-1)^2}=\dfrac{4^2}{2^2}=\dfrac{16}{4}=\dfrac{4}{1}$$.
Question 7
1 / -0

In Young's double slit experiment if the slit width is in the ratio $$ 1: 9$$. The ratio of the intensity at minima to that at maximum will be

A
$$1:1$$

B
$$1:9$$

C
$$1:4$$

D
$$1:3$$

Solution

Amplitude of light from a slit of width d $$\propto \sqrt{d}$$
Hence $$\dfrac{A_1}{A_2}=\sqrt{\dfrac{1}{9}} =\dfrac{1}{3}$$
$$\implies A_2=3A_1$$
Thus the ratio of intensity at minima to that at maxima $$=\dfrac{(A_2-A_1)^2}{(A_2+A_1)^2}$$
$$=\dfrac{2^2}{4^2}=\dfrac{1}{4}$$
Question 8
1 / -0

Astronomers can tell whether a star is approaching or receding from the earth . Identify by which of the following method they can predict this ?

A
Absorption spectra of the star

B
Doppler shift of the starlight

C
Temperature of the star

D
Brightness of the starlight

E
Thermal signature of the star

Solution

To predict the movement of a star, we compare the spectra of elements found in star (H, He Na etc.), first spectra which are obtained from star and second spectra from laboratory. If spectral lines of the spectra obtained from star, are shifting towards red end (called red shift) then star is going away from earth and if shifting is towards blue (called blue shift), then star is approaching the earth. This is Doppler's shift.
Question 9
1 / -0

Red light passes through two narrow vertical slits so that a diffraction pattern is formed on a screen.
Which of the following looks most like the expected diffraction pattern?

A

B

C

D

E

Solution

As the slits are narrow and vertical. The diffraction pattern will be two thin vertical parallel lines.
Question 10
1 / -0

The size of corpuscles are ________ for different colours.

A
same

B
different

C
either (a) or (b)

D
None of these

Solution

Different.
The corpuscles can be of different sizes. The different colors of light are due to the different sizes of the corpuscles.